#include <stdio.h>
#include <time.h>
#include <math.h>

int frequency_of_primes(int n){
    int i,j;
    int freq = n-1;
    for(i=2;i<=n;i++)
        for(j=sqrt(i);j>1;j--)
            if(i%j==0){
                freq--;
                break;
            }
    return freq;
}

int main(){
    clock_t t;
    int f;
    t = clock();
    printf("Calculating...\n");
    f = frequency_of_primes(9999);
    printf("The number of primes lower than 100,000 is : %d\n",f);
    t = clock() -t;
    printf("It took me %d clocks(%f seconds).\n",t,((float)t)/CLOCKS_PER_SEC);
    return 0;
}